Kai (18), obedience to women

Kai's alarm sounded, causing him to roll over and hit the snooze button. This didn't work. Instead a female voice came called out "Get out of bed!"
Kai found himself instantly bolting up right, throwing the covers off and pushing himself out of bed.
"Huh?" he thought to himself. He was never eager to leave the comfort of his bed, what was so different about this morning. He looked back down to his alarm clock. He had to look twice. this wasn't his usual alarm.

Suddenly the same female voice cried out, Kai noticed that it was coming directly from the alarm clock.
"Now, strip down and go get showered! Don't take too long!" the voice was enthusiastic. Without hesitation, Kai pulled down his pajama bottoms, followed by his shirt. Finally he stepped out of his underwear, leaving himself completely nude.
"What is going on?!" Kai questioned. He never stripped before reaching the bathroom, just in case his sister saw him. She would always tease him about his cock, even though she had never seen it. Or, at least he thought she hadn't. Now however, he was reaching for his bedroom door, ready to walk down the hall baring all.

Kai slowly crept down the hall, using his hands to cover his private parts. Looking to his left to check to see the coast was clear before looking back to the right. He breathed a sigh of relief whilst reaching for the bathroom door.
"Stop" his sister cried out behind him, the boy obeyed, not sure why he was doing so.
"What are ya doing Kai?" his sister teased.
"I'm going to shower Millie!" he snapped back, he wanted to reach for the door and get into the safety of the bathroom, but he couldn't get himself to move.
"Woah, Kai, don't take that tone with me!" Mille teased, "Oh, and turn and face me when you speak to me!"

Kai swung around with a sense of massive unease, standing facing his sister. Millie was 22 years old, brunette with shoulder length hair. She was drop dead gorgeous, but to Kai, she was the anti-christ. She stood there, staring back at Kai, raising her eyebrows at the fact he was still stood covering his private area.
"I think you should put your hands on your head Kai!" she laughed.
Kai obeyed, revealing his penis to his sister. He was shell shocked. Why was he doing this?#

"Oh, thats nice Kai! Its a little bit small though!" Millie continued to laugh, whilst pointing. Kai just stood there, with his hands firmly on his head.
"Put your hands back down by your side and smile for me!" Kai continued to obey, smiling back to his sister, who at this point had pulled her phone out. Kai was frozen, smiling, as his sister's phone flashed.
"Cheers Kai! I'll cherish that photo! You can go shower now!"

The boy quickly turned back around, red faced and humiliated. What was happening?